What is the system of communication that involves an alphabet in which letters are represented by combinations of long and short signals of light or sound?
A
Email
B)
Morse code
Binary code
D
Digital Signal Reception
Wireless intern

B)

Morse code

Explanation:

Morse code is a communication system developed by Samuel Morse, an American inventor, in the late 1830s. The code uses a combination of short and long pulses – dots and dashes, respectively – that correspond to letters of the alphabet.

b

Explanation:

I got it right on the exam. Morse code is your answer.

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-